A system of this type is known from DE 20 30 591 C3 wherein, at the horizontally movable transport vehicle, there are attached gripping means which are able to grip and release transport baskets. The transport baskets can be moved horizontally and picked up and deposited vertically by means of the transport vehicle. Underneath the guiding means for the transport vehicle there are arranged treatment machines and treatment chambers which can be flooded with liquid and into which transport baskets can be inserted. The treatment chambers are provided with receiving devices for the transport baskets which are provided with suitable rotary driving means. Furthermore, DE 34 20 859 C2 proposes treatment machines of the above-mentioned type wherein the receiving devices for the transport baskets with the respective rotary driving means can be pivoted around a horizontal axis to ensure that the large quantity of parts circulates in the liquid.
There are also prior art systems wherein the horizontally drivable transport vehicle is provided with gripping means for transport baskets, which gripping means comprise lifting and lowering means and their own rotary driving means for the transport baskets. Underneath the transport path of the transport vehicle there are arranged tanks which contain treatment liquid and into which the transport baskets can be lowered by lifting and lowering means. After the transport baskets have been plunged underneath the surface of the liquid, the transport baskets are driven at a slow speed around a vertical axis and subsequently lifted out of the tank in a dripping-wet condition and moved on by the transport vehicle. As a result, treatment liquid is wasted and the contents of subsequent tanks are polluted.
From DE 42 17 615 A1, there is known a system wherein a transport vehicle moves on a single rail track which is attached to a ceiling. The transport path of the transport vehicle extends across a number of treatment containers which can be filled with a liquid. At the transport vehicle there is attached a suspended holding device for receiving transport boxes via two pairs of chain pulleys which can be wound up or unwound by two independent lifting devices. The freely suspended holding device is provided with two journals which are positioned opposite one another and which can be moved into two opposed V-shaped supports which are firmly attached to the edges of the treatment containers. The transport boxes are freely inserted into the suspended holding devices. By operating the lifting devices in opposite directions, the suspended holding device can be tilted to and fro by the pairs of chain pulleys in order to re-position the mass-production parts in the transport boxes. In a lowest position in which the suspended holding device is positioned inside a treatment container, optionally underneath a liquid level, the suspended holding device is tiltably supported in the V-shaped supports, and in a higher position above the treatment container, it freely oscillates from the pairs of chain pulleys. In this higher position, the treatment liquid can merely be allowed to drip off in order to prevent same from being carried off and wasted.